The danger of people being trapped on the first floor of a building has long been recognised and various proposals have been made to provide a collapsible ladder which can be stored easily and which does not assist unauthorised entry into the building by being permanently extended.
Some ladders have been variations of rope ladders or chain ladders. Such ladders have the problem of instability in that they tend to swing to and fro and from side to side, making them difficult to use by the very young, the elderly or the infirm.
It is desirable for this reason to form a ladder of rigid stiles and the prior art discloses ladders in which the stiles are foldable or telescopically collapsible. Examples of foldable ladders are to be found in GB-2176831 which shows a ladder in which the stiles are formed by lazy-tongs and in GB-2153423 in which the stiles are hinged about pivotal axes extending at right angles to the plane of the ladder, the stiles being hinged to the rungs and being foldable half way between each pair of rungs.
Though relatively rigid in one plane, such ladders are still flexible in other planes and can present difficulty in use. Furthermore, such ladders can only be used when suspended from above and cannot be used in any application other than as a fire escape.
GB-2233022 describes a step ladder with telescopically collapsible stiles. The rungs of this ladder have on their under-side latch mechanisms including resiliently biased pins which engage in holes in the stiles to lock the stiles in an extended position. A cord connected to the pins is also engaged by a button centrally mounted on the rung. When the button is depressed, it pulls on the cords and retracts the pins from the holes in the stiles, to allow the sections to be collapsed into one another.
The disadvantage of this ladder is that the button on each rung in turn must be depressed to allow the sections to be collapsed one at a time, thus making the collapsing of the ladder a time consuming process.
GB-2110286 describes a ladder in which the stiles incorporate studs on resilient levers mounted externally on the stiles. An eccentric formed on the lower end of the stile sections is proposed for bringing about automatic release. When the uppermost section of the stiles is collapsed, then as it reaches its lowermost position, it releases the next lower section thereby enabling the ladder to be collapsed from the top downwards.
This construction is costly to implement and has the further disadvantage that it is difficult to collapse the ladder on account of the fact that the ladder must be collapsed from the top downwards. As one must be standing on the ladder to reach the top rung, this means that one must either be standing on the ladder to collapse it or one must lie the ladder on the ground, which may not always be possible in the space available.